The Northern Andes boundary is a first-order tectonic structure in Colombia with historically M>7 earthquakes. However, details about the individual sections of the system remain unknown. We illuminate the seismotectonic of the Algeciras fault by investigating an earthquake sequence that started on December 24, 2019. Using recent seismic networks of the region, we estimate focal mechanisms of the foreshocks and aftershocks, local stress field, kinematic slip models of the largest events, and Coulomb stress changes. Two mainshocks (a doublet of Mw 6.0 and 5.8) occurred within 16 minutes, rupturing just a few kilometers from each other. Discrimination of causative faults among the centroid moment-tensor nodal planes is difficult because the focal zone is a complex tectonic environment. We reinterpret local faults using geologic information, geomorphology and combine this new information with seismology results. The relocated aftershocks show a cluster with an L-shaped pattern concentrated in a ~7 km x 7 km area. Our model defines the Algeciras fault with two structural styles merging to the Guaicáramo Fault System and border the Eastern Cordillera to the east, supporting its regional dextral and transpressional kinematics. The NW part is characterized by a duplex-style of right-lateral strike-slip with inner secondary faults of the same sense or movement, and the SE zone by a domino-style system with inner minor faults of sinistral kinematics. The earthquake doublet is a part of the duplex style, whereas, the south part of the aftershocks is located on the domino-style, of the northern termination of the Algeciras Fault System.

South Asia is among the most populous regions of the earth which houses fast-developing economies. The unique geographical settings and socio-economic-demographic structure of the region make it highly vulnerable to the risks posed by climate change as documented by several comprehensive scientific research reports. Human-induced climate change signatures have already been noted in the form of increasing extremes (e.g. cyclones, droughts, floods, heat waves, thunderstorms, etc.), rising sea level, and changing monsoon patterns over the region. Though considerable progress has been made towards understanding the science of climate change, regional climate change consequences are still not well understood and limited by sparse observational networks and inadequate knowledge of region-specific physical processes which often lead to large spread and uncertainties in model projections. Based on the available literature, the chapter highlights the past, present, and future projections of climate over South Asia. Recent advances in observations and dedicated regional and earth system modeling activities over the region are also discussed alongside other emerging methodologies and tools which can lead to overall improvement in understanding of physical processes. We discuss the studies that have been carried out in the past and also the prospective gap areas that can be pursued in future through the use of a combined framework of modern observations-modeling-analysis techniques.

Mid-Tropospheric Cyclones (MTCs) are moist synoptic systems with middle tropospheric vorticity maxima and little or no signature in the lower and upper troposphere. Apart from a few case studies over South Asia, the occurrence of MTCs in other parts of the tropics has not been explored. Here, we present MTC statistics over the globe (50 N - 50 S) using 20 years of MERRA-2 reanalysis data and compare them with monsoon lows, depressions, and tropical cyclones (together referred to as lower troposphere cyclones; LTCs). Automatic cyclone center detection on the 600 hPa geopotential height field is used to detect synoptic cyclone centers. Based on vertical profiles of vorticity, the detected systems are classified as MTCs or LTCs. We find that synoptic mid-level moist vorticity maxima are not limited to South Asia and are found over most of the globe’s monsoonal regions. Apart from South Asia (Arabian sea, Bay of Bengal, and South China sea), MTCs are observed over the west and central Africa, eastern and western Pacific during the boreal summer. In the boreal winter, regions that support MTCs include northern Australia, the southern Indian Ocean, and South Africa. All these regions show monthly, as well as inter-annual variability in MTC and LTC activity. In particular, most regions show high MTC center density early in the monsoon and relatively high LTC activity during respective primary monsoon months. In both hemispheres, MTCs are more prevalent nearer to the equator and usually coincide with regions of cross-equatorial low-level monsoon flow. LTCs, on the other hand, are more common further polewards, usually within the monsoon trough itself. Finally, the global tropical probability distribution of the difference between middle and lower level vorticity versus the height of peak vorticity is bimodal; one peak corresponds to MTCs at about 600 hPa while the second 900 hPa corresponds to LTCs. Thus, tropical moist cyclonic systems naturally tend to reside in either the MTC or LTC category.

In the paper double seismic zones are discussed as a phenomenon confirming penetration of oceanic lithosphere through the mantle as solid and extremely hard medium. Formation of such medium has been performed by solidification of Earth from core-mantle boundary upwards. Lower mantle formed under extremely high pressure prevents any earthquakes. Upper mantle is suitable for formation of embrittlement and earthquakes in double seismic zones. Continental lithosphere overriding oceanic lithosphere forms subducton zones firmly anchored in mantle. Deeply steeping subduction zones penetrate mantle burning its way by melting probably as far as through core-mantle boundary. Oceanic lithosphere grows in midocean ridges with half speed of the front of plate. Driving forces are tides. Movements of plates confirm hotspot tracks. Hotspots are probably of meteoric origin. They penetrate through mantle in same way as subducton zones. Material created in penetration moves upwards by buoyancy and during its subsidence creates hotspot tracks over 10 000 km, however their penetration as far as coremantle boundary is not proven.

We present a novel approach to model hydro-chemo-mechanical responses in rock formations subject to fracture propagation within chemically active rock formations. The developed framework integrates the mechanisms of reactive transport, fluid flow and transport in porous media, and fracture propagation in poroelastic media using the phase-field model. The solution approach integrates the geochemical package PHREEQC with a finite-element open-source platform, FEniCs. Thereby, the PHREEQC solver is used to calculate the localized chemical reaction, including solid dissolution/precipitation. The resulting solid weakening by chemical damage is estimated from the reaction-induced porosity change. The proposed coupled model was verified with previous numerical results and applied to a synthetic case exhibiting hydraulic fracturing enhanced with chemical damage. Simulation results suggest that mechanical failure could be accelerated in the presence of ongoing chemical processes due to rock weakening and porosity changes, allowing the nucleation, growth, and development of fractures.

Distributed Acoustic Sensing (DAS) leverages an ocean-bottom telecommunication fiber-optic cable into a densely-sampled massive array of strain sensors. We demonstrate DAS applications to Passive Acoustic Monitoring (PAM) through an experiment in Longyearbyen, Svalbard, Norway. We show that DAS can measure many types of signals generated by dynamics in the atmosphere, ocean, and solid earth. These include primary and secondary microseisms, Scholte waves, water-layer acoustic resonances, and seismic waves from earthquakes. In addition, we can trace the origin of primary microseisms back to distant storms a quarter of the way around the planet. We also find that the fjord acts as an amplifier for microseisms. Because DAS is capable of hydroacoustic monitoring with high spatial resolution over great distances, it can deliver great scientific value to ocean observation. We believe that DAS can and will become a valuable component of the Global Ocean Observing System.

Recently a polynomial reconstruction technique has been developed for reconstructing the magnetic field in the vicinity of multiple spacecraft, and has been applied to events observed by the Magnetospheric Multiscale (MMS) mission. Whereas previously the magnetic field was reconstructed using spacecraft data from a single time, here we extend the method to allow input over a span of time. This extension increases the amount of input data to the model, improving the reconstruction results, and allows the velocity of the magnetic structure to be calculated. The effect of this modification, as well as many other options, is explored by comparing reconstructed fields to those of a three-dimensional particle in cell simulation of magnetic reconnection, using virtual spacecraft data as input. We often find best results using multiple-time input, a moderate amount of smoothing of the input data, and a model with a reduced set of parameters based on the ordering that the maximum, intermediate, and minimum values of the gradient of the vector magnetic field are well separated. When spacecraft input data are temporally smoothed, reconstructions are representative of spatially smoothed fields. Two MMS events are reconstructed. The first of these was late in the mission when it was not possible to use the current density for MMS4 because of its instrument failure. The second shows a rotational discontinuity without an X or O line. In both cases, the reconstructions yield a visual representation of the magnetic structure that is consistent with earlier studies.

Sustained periods of southward interplanetary magnetic field can result in strong magnetospheric convection, during which, the Alfven layer, separating regions of sunward convection and closed drift paths, migrates earthwards. Plasmasheet electrons then have direct access to the inner magnetosphere, traversing the dawn sector before crossing the magnetopause, and present a potential seed population for the radiation belts. Here we examine, for the first time, whether energetic electrons can be sufficiently energised during their drift, via resonant interactions with whistler-mode chorus waves, so as to pass the Alfven layer prior to leaving the system. We utilise a natural coordinate system for magnetosphere convection, (U,B,K) space, in which we calculate the drift trajectories, electron energies on open drift paths, and drift times. The acceleration time from resonant chorus-wave particle interactions is calculated using the Versatile Electron Radiation Belt model (VERB) first as a 2-D diffusion equation and then in 4-D convection-diffusion mode. Comparing the drift times to the acceleration timescales we find that interactions with chorus waves do result in a portion of the electrons on open drift paths passing the Alfven energy. However, whether this acceleration occurs sufficiently quickly depends on the energy distribution of the electron population.

Land management activities that provide higher soil organic carbon stimulate microbial activity and enzymatic reactions. Riparian forest, agroforestry, and row-crop agriculture treatments are among common land-use systems in the lower Missouri River Floodplain (MRF) region in New Franklin, MO. The study of soil enzyme activities under different land use in this region is of importance for monitoring soil quality and evaluation of climatic changes on soil health. This investigation aimed to characterize soil properties such as soil C and N, porosity, moisture content under three-land use (agroforestry, riparian forest, and agriculture) and correlate their influence on soil microbial communities and enzyme activities. Soil samples were collected from the three land management systems, and enzyme activity was measured in three seasons of Fall 2019, Summer 2020, and Spring 2021. Results revealed significantly higher levels of β-glucosidase, β-glucosaminidase, and dehydrogenase activity in agroforestry (AF) and riparian forest (RF) treatments relative to agriculture (AG) management in all three studied seasons. Dehydrogenase activity was higher (p<0.0001) in RF relative to AF and AG sites. Efforts to incorporate perennial management systems in river-floodplain landscapes will help increase organic matter content, which stimulates microbial diversity and soil enzyme activity as well as improving the performance of conservation buffers. The study concluded that tree-based AF systems enhance soil physicochemical and biological properties.

Megathrust earthquakes impose changes of differential stress and pore pressure in the lithosphere-asthenosphere system that are transiently relaxed during the postseismic period primarily due to afterslip, viscoelastic and poroelastic processes. Especially during the early postseismic phase, however, the relative contribution of these processes to the observed surface deformation is unclear. To investigate this, we use geodetic data collected in the first 48 days following the 2010 Maule earthquake and a poro-viscoelastic forward model combined with an afterslip inversion. This model approach fits the geodetic data 14% better than a pure elastic model. Particularly near the region of maximum coseismic slip, the predicted surface poroelastic uplift pattern explains well the observations. If poroelasticity is neglected, the spatial afterslip distribution is locally altered by up to ±40%. Moreover, we find that shallow crustal aftershocks mostly occur in regions of increased postseismic pore-pressure changes, indicating that both processes might be mechanically coupled

Watershed hydrological processes controlled by subsurface structures that have hierarchical organization across scales, but there is a lack in multiscale model validation. In this study, using a comprehensive dataset collected in the forested Shale Hills catchment, we tested the series HYDRUS codes (i.e., HYDRUS-1D at the pedon scale, HYDRUS-2D at the hillslope scale, and HYDRUS-3D at the catchment scale) that included a hierarchical multi-dimensional modeling approach for water flow simulation in the vadose zone. There is good agreement between 1D simulations and measurements of soil moisture profiles controlled by soil hydraulic parameters and precipitation characteristics; however, short-term fluctuations in preferential flow were poorly captured. Notably, 2D and 3D simulations (Nash–Sutcliffe efficiency, ), which accounting subsurface preferential flow controlled by slope positions and shallow fractured bedrock, provided better results than 1D simulations (). Our modeling approach also illustrated that the studied watershed was characterized by weathered and un-weathered fracture bedrocks, which routed water through a network of subsurface preferential flow pathways to the first-order stream. Furthermore, a dual-porosity or anisotropy model produced more accurate predictions than a single-porosity or isotropy model due to a more realistic representation of local soil characteristics and layered structure. Our multi-dimensional modeling approaches credited with diagnosing and presenting the dominant hydrological processes and the interactions within soil-landscape features across one sloped catchment.

A few MHD simulations have been performed to study the interaction between a propagating interplanetary shock and Earth's standing bow shock, followed by the magnetosheath and magnetopause. They satisfactorily explain the deceleration of the interplanetary shock in the magnetosheath, which was observed a few dozen times by well-arranged satellites. In this work, we perform a hybrid particle-in-cell simulation in a similar setting with a self-consistently developed quasi-perpendicular interplanetary shock. We track the position of the interplanetary shock as it travels through the magnetosheath. We show that early in the propagation through the magnetosheath, the interplanetary shock slows down, which is in line with the conclusion of previous studies. Later in the propagation, however, we find that -- in the plane perpendicular to the interplanetary magnetic field -- the interplanetary shock travels faster inside the magnetosheath than it does in the solar wind. We also note that as the magnetic field lines are stretched along the magnetopause, the interplanetary shock becomes quasi-parallel close to the magnetopause.

Data-processing methods only considering the turn-off ramp in transmitting waveforms are well established for land-based transient electromagnetic (TEM) methods. The turn-on ramp effects on late-time responses are generally neglected by data-processing methods. Our forward-modeling results of homogeneous half-space models show that the full-waveform effect which includes both effects caused by turn-on and turn-off stages is common for a wide range of conductivities. The inversion results for synthetic and field examples illustrate that the inversion algorithm which does not consider the full-waveform effects can lead to a higher resistivity in deeper parts of recovered models compared with the true model. Therefore, it is of vital importance to account for the full waveform effects in both forward modeling and inversion algorithms. We use synthetic examples to show how our inversion algorithms can improve the recovered model, and use real-data examples to show the importance of incorporating full transmitting waveforms in data-processing procedures.

Accurate numerical modeling of fracture propagation and deflection in porous media is important in the development of geo-resources. To this end, we propose a novel modeling framework to simulate nonplanar three-dimensional (3-D) fracture growth within poroelastic media, using an iteratively coupled approach based on time-/scale-dependent fracture stiffness. In this approach, the propagating fractures are explicitly tracked and fitted at each growth step using triangular elements that are independent of the matrix discretized by hexahedral grids. The finite volume/finite element method (FVFEM) is employed to solve the hydro-mechanical system, based on the embedded discrete fracture model (EDFM). The calculated pressure in fractures and the stress state of the host grid of the embedded fractures constitute the boundary conditions for the boundary element method (BEM). The BEM module, in turn, renders the evolving fracture stiffness and aperture for the FVFEM module. Finally, the total stresses and the fracture-tip displacements are computed at the end of each time step to estimate the velocity and direction of newly created fractures ahead of the fracture tip. The proposed model is first validated against analytical solutions. Then, in three different examples, results are shown from the fracture’s footprint under layered stress conditions, simultaneous propagation of two nonplanar 3-D fractures, and the mechanical interaction of en échelon arrays. This work presents an efficient framework to simulate propagation of nonplanar fractures, and establishes the foundation to build an integrated simulator for fracture propagation, proppant transport, and production forecasting in unconventional formations.

A methane gas infilling fault theory is presented to refine and upgrade the conventional earthquake theory of elastic rebound of active geological faults. It adds the infilling of highly compressed methane gas mass into the deep geological fault zones. Such gas infilling makes the fault active and accumulate the elastic energy. With time, the gas in the fault traps has more and more mass and high and high pressure. The gas pressure can rupture the trap along the geological fault and release some gas mass to migrate along the fault, which causes tectonic earthquakes. The theory shows that the earth-quaking process is a cooling process because of gas expansion. The earthquake magnitude estimated from the seismic waves can have a quantitative relationship with the gas volume from the trap is quantified. The theory can explain mega earthquakes along subducton zones.

In this paper, we present the variations of IMF-Bz, Solar wind Parameters (Vsw, Nsw, and Psw), and Geomagnetic Indices (AE and SYM-H), and the variation of Vertical Total Electron Content (VTEC) using simultaneous VTEC data from 12 GPS-TEC stations over the Indian, Australian, Brazilian and South African regions. We describe contrast in Total Electron Content (TEC) throughout the globe using global ionospheric maps at regular 2-hour interval of UT during the three intense geomagnetic storms. Moreover, we observed that heavily TEC influenced areas were found to be transposing through equatorial plane starting from eastern sectors to the western sectors. Indian Ocean, Atlantic Ocean and South Pacific Ocean sectors were affected flowingly. Global Ionospheric Maps evince that Indian and Brazilian sectors were affected heavily explaining the TID and Equatorial Anomaly as seen on those areas. The equatorial and low-latitude regions have been mainly affected by the geomagnetic storms. All these results suggested that the acute disruption of global winds (surging towards the equator from higher latitudes) and electric fields commenced from magnetosphere-ionosphere interaction cause the severe modification in the equatorial, low-latitude region. We checked the cross correlation during the period of high solar and geomagnetic activities; the correlation gradually increased with the near by stations by latitudes in most of the cases which was another intriguing result. the storms were affected globally which is why we believe that variation of TEC over various stations of the globe could turn out to be very helpful in predicting solar wind coupling with magnetosphere-ionospehere.

There have been important criticisms of IPCC recent reports for failing to communicate the dire nature of the current predicament facing civilization – so-called “scientific reticence” – as well as for assuming functional, planetary-effective scale biomass carbon capture and storage in its survivable scenarios [1-3]. In the light of major reports released in 2018 [4,5] which underscore the discrepancy between the current climate trajectory and best-case requirements to maintain global civilization, the current predicament is often described as an “existential” crisis [6]. Part of the confusion appears to stem from the lack of discussion of specific scenarios, such as rapid arctic methane release [7,8], which are not discussed by the IPCC in proportion to their catastrophic potential. This scenario is briefly examined using the Goddard Institute for Space Studies (GISS) ModelE v2 7.50.05 [9]. It is suggested that the results presented here represent a lower bound to climate disruption since in this set-up, neither the oceans nor arctic sea ice (a significant and ongoing runaway feedback [10]) respond to the changes modeled; namely, a sudden release of stored methane gas.

Imagery from the GOES series has been a key element of U.S. operational weather forecasting for four decades. While GOES observations are used extensively by human forecasters for situational awareness, there has been limited usage of GOES imager data in numerical weather prediction (NWP), and operational data assimilation (DA) has ignored cloud and precipitating pixels. The motivation of this project is to bring the benefits of GOES-R Series enhanced capabilities to advance convective-scale DA for improving convective-scale forecasts. We have developed a convolutional neural network (CNN) prototype, dubbed “GOES Radar Estimation via Machine Learning to Inform NWP (GREMLIN)” that fuses GOES-R Advanced Baseline Imager (ABI) and Geostationary Lightning Mapper (GLM) information to produce maps of synthetic composite radar reflectivity. We find that the ability of CNNs to utilize spatial context is essential for this application and offers breakthrough improvement in skill compared to traditional pixel-by-pixel based approaches. Making use of ABI spatial information potentially provides benefits over radiance assimilation approaches that are limited by saturation of radiances in pixels with precipitation. This presentation will briefly describe the GREMLIN model and characterize its performance across meteorological regimes. We are developing a dense neural network (DNN) to produce vertical profiles of radar reflectivity and latent heating based on the two-dimensional fields output from GREMLIN. The resulting three-dimensional fields of latent heating will be used to initialize NWP simulations of convective-scale phenomena. Another DNN will be developed to produce uncertainty estimates of latent heating for each pixel. Our approach for data assimilation will be described and is innovative in being the first-time machine learning (ML) will be used for the nonlinear latent heating observation operator in the NOAA hybrid Gridpoint Statistical Interpolation (GSI) and/or JEDI systems. The approach will provide all the elements of the Jacobian needed for GSI DA and has the advantage of automatically maintaining the tangent linear and adjoint models through finite difference mathematics.